usb: chipidea: msm: Add device tree binding information

Document device tree binding information as required by
the Qualcomm USB controller.
Signed-off-by: Peter Chen <peter.chen@freescale.com>
Signed-off-by: Ivan T. Ivanov <iivanov@mm-sol.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Documentation/devicetree/bindings/usb/ci-hdrc-qcom.txt

+Qualcomm CI13xxx (Chipidea) USB controllers
+
+Required properties:
+- compatible:   should contain "qcom,ci-hdrc"
+- reg:          offset and length of the register set in the memory map
+- interrupts:   interrupt-specifier for the controller interrupt.
+- usb-phy:      phandle for the PHY device
+- dr_mode:      Should be "peripheral"
+
+Examples:
+	gadget@f9a55000 {
+		compatible = "qcom,ci-hdrc";
+		reg = <0xf9a55000 0x400>;
+		dr_mode = "peripheral";
+		interrupts = <0 134 0>;
+		usb-phy = <&usbphy0>;
+	};